1. Field of the Invention
The present invention relates generally to an apparatus for severing a slide fastener chain, and more particularly to an apparatus for automatically severing a slide fastener chain having a succession of fabric pieces attached to each of the opposed longitudinal marginal edges thereof into a plurality of slide fasteners of an individual length.
2. Description of the Prior Art
According to the related art, it is customary to first sew a succession of fabric pieces such as trouser flies to a continuous length of a slide fastener chain along its one longitudinal marginal edge, with gap portions interposed between each adjacent pair of fabric pieces, while the continuous slide fastener chain is fed along a feed path; to detect such inter-fabric-piece gap by means of detecting means during the feeding of the fabric-pieced continuous slide fastener chain; and to finally, upon receipt of a signal generated by the detecting means, sever the continuous slide fastener chain laterally across the gap portions into a number of slide fasteners of an individual length each having a fabric piece attached to its one longitudinal marginal edge. This method and some apparatuses to carry out the method are disclosed in Japanese Patent laid-open publication No. 48-42844 and Japanese Patent Publication No. 1-44421. In this method, since only one succession of the fabric pieces are sewn to only one longitudinal marginal edge, mere cutting of the slide fastener chain across between each adjacent fabric pieces on only one longitudinal edge provides a multiplicity of slide fasteners of individual length, yet without involving any risk of erroneous severing across fabric pieces leading to damaging of the products.
However, in attaching slide fasteners to such articles as garments like one-piece dresses, blanket covers, fabric sacks and fabric bags, two successions of fabric pieces composing such articles mentioned above must be sewn one to each longitudinal marginal edge of a slide fastener chain; and then the slide fastener chain is severed laterally across the gap portions. However, this operation suffers from a problem. Fabric pieces to be sewn to the slide fastener chain are not necessarily formed uniform in length. The longer are fabric pieces to be used, the more do they vary in length from each other, naturally. Besides, the operation of sewing fabric pieces to a slide fastener chain is carried out at very high rate for enhancement of production efficiency. With such high-speed operation, fabric pieces are not necessarily sewn to the opposed longitudinal edges of the slide fastener at right positions or with the opposed mating fabric pieces laterally in registry. This means that the opposed mating gap portions interposed therebetween are liable to become out of alignment with each other. The severing of the slide fastener chain across one gap portion under this condition would objectionably cut across the fabric piece, instead of gap portions.